Intraoral dental radiology has been utilized by dentists and oral surgeons for many years in order to obtain images of a patient's teeth, mouth and gums to aid in intraoral diagnosis and treatment. In conventional radiology, a photographic film is positioned in a patient's mouth, for instance, behind his teeth, and an x-ray beam is projected through the teeth onto the film. The film is developed in a dark room or using special chemicals to obtain a viewable photographic image of the teeth.
Several drawbacks are associated with the conventional imaging process described above. In particular, the patient is required to bite down on the photographic film holder for a period of time, which can be uncomfortable, and sometimes even painful, for instance, when the photographic film gouges the gums of the patient, and often causes the patient to experience a gag-reflex. Additionally, the developing process is a time consuming and costly process. Moreover, the photographic film, which is essentially a flat plate, is does not fit the curvature of the dental arch without being bent, thereby resulting in distorted exposures, particularly at the edges of the film. Furthermore, in many cases the film does not fit into the mouth of the patient at the desired location, thereby preventing the possibility of obtaining any images at all of particular teeth or at a particular angle.
In recent years, filmless (or, digital) dental radiology has started replacing the conventional methods of intraoral diagnosis and treatment. Although an x-ray beam is still projected through the patient's teeth, an electronic sensor is placed behind the patient's teeth instead of a photographic film.
There are two main types of systems that are typically used in digital dental radiology. The first, known as a Direct Digital Radiography System, utilizes a sensor and a cord connected to a computer and a monitor to display the digital x-ray image thereon. These systems utilize a flat rigid sensor containing a Charge Coupled Device (CCD) covered with radiation sensitive receptors. Quality images or pictures, similar to developed conventional x-rays, appear instantly on the monitor screen. The images can be stored electronically and printed and or transferred electronically if desired. This technology eliminates the need for film and a dark room (and/or chemicals) as well as the need for a time consuming development process. Additionally, since the electronic sensor is much more sensitive to x-rays than is film, the dosage of radiation that is transferred to the patient may be significantly lowered.
However, the sensors utilized in Direct Digital Radiography Systems have complicated electronic circuitry or chips to correct image distortions that occur due to the flat surface of the sensor with respect to the curved dental arch, as well as to convert the image data to readable format prior to transferring to the display device. Therefore, obtaining and operating Direct Digital Radiology equipment is expensive, as it can cost thousands of dollars, which can be prohibitive to many dental practitioners. Furthermore, depending on its size, the hard sensor may not fit in some locations in the oral cavity.
The second main type of digital system, known as an Indirect Digital Radiography System, may be cordless, and utilizes a storage phosphor transfer image plate, which, after scanning, integrates digitally into a computer and displays the image on a monitor. When exposed to a radiation beam the storage phosphor imaging plate holds an image, which is electronically processed via software to produce the digital image. The smaller size and lack of a cord as compared to the direct system, along with the slight flexibility of the plate, make intraoral placement of phosphor plates easier than that of direct system sensors. Additionally, the elimination of the need for film and a dark room (and/or chemicals) as well as the development process saves in development time of the images. As in direct systems, radiation may be reduced significantly compared to conventional x-ray techniques.
Disadvantages associated with indirect systems, relative to direct systems, include the extra time required to scan and erase the plates. Moreover, the equipment required for indirect systems is very costly, particularly the scanner, which is prohibitive to many dental practitioners.
The DenOptix® Photostimulable Phosphor Plate, manufactured by Gendex, utilizes an elastic phosphor plate for indirect dental radiography. The Gendex phosphor is powder-based and is therefore limited in maximum thickness to 0.3 mm, since for higher thicknesses the light scattering during the scanning process becomes too high, and a lot of light is lost. Also, the light scattering reduces the spatial resolution. Moreover, the Gendex product requires an expensive and bulky scanner, costing tens of thousands of dollars.
There have been several attempts to overcome the problems involved with digital radiography, however, each comprise limitation of its own.
U.S. Pat. No. 3,622,785 discloses a fluoroscopic unit suitable for intraoral use. A phosphor coating is deposited on the face at the tip of a curved fiber optic bundle adapted for placement within the mouth. In response to low x-ray radiation, a low-level image is formed. The image is transmitted through the fiber optic bundle to an image intensifier, which amplifies the image to above the visual threshold, and the image is displayed on a monitor. Although the fiber optic bundle is curved, and may be flexible, since the face of the fiber optic bundle tip is flat, distortion of the image will likely occur. However, U.S. Pat. No. 3,622,785 does not recognize this limitation and therefore does not teach any method of correcting the distorted image. Moreover, in U.S. Pat. No. 3,622,785 the practitioner must hold the unit by hand while directing the fiber optic bundle, and thereby be exposed to radiation in the process.
JP 1170443 discloses a dental arch shaped detector connected to a microcomputer for generating an image of the entire jaw. The detector is bitten by the patient, and when the electrodes are brought into contact with the teeth, current flows between the electrodes. When a change in current is detected, the portion of the detector bitten by the teeth sends data to the microcomputer. The device of JP 1170443 comprises complicated electronics, which adds undesirable costs to the purchase and operation of the system.
US 2005/0226389 discloses an anatomically conforming intraoral dental radiographic sensor comprising two abutted imaging planes having an angle of 20-40 degrees between them. According to US 2005/0226389, this arrangement results in significantly more patient comfort than that provided by a single flat plane of equivalent imaging area. Fiduciary elements are situated on the sensor for marking the field of view. Image distortions caused by non-perpendicularity of the illuminating x-ray beam relative to the surface of the radiation detector are corrected by known mathematical calculations. However, in order to correct the distortions, complicated electronics must be provided, which adds undesirable costs to the purchase and operation of the system. In Addition, this patent is directed to correction of mainly vertical distortion.
U.S. Pat. No. 6,652,141 discloses an oral sensor configured to fit close to a target area in an oral cavity. The sensor is a filmless radiography system that transmits data to a preprocessor via a cable, and then to a display device. The sensor comprises a housing having a lower section and an upper section. The upper section is configured with a cable connector which receives the electrical cable that connects to the printed circuit board of the sensing structure. As seen in FIG. 10 of U.S. Pat. No. 6,652,141, the cable connector juts out toward the center of the oral cavity. Moreover, the upper and lower housing sections comprise a substantial thickness, relative to the typical size of the oral cavity, which, when combined with the cable connector create a sizeable object. When situated in the oral cavity, the patient will find such an object disturbing and uncomfortable, similar to the problem that exists in most intraoral products.
It is therefore an object of the present invention to provide an intraoral digital x-ray apparatus, which allows the dental practitioner to obtain digital intraoral images, and overcomes the drawbacks associated with the prior art, including high costs and discomfort.
It is an additional object of the present invention to provide an intraoral digital x-ray apparatus that provides an undistorted image, which therefore does not require expensive and/or complicated electronics to correct a distorted image prior to display.
It is an additional object of the present invention to provide an intraoral digital x-ray apparatus that is comfortably situated in the oral cavity of a patient.
It is an additional object of the present invention to provide an intraoral digital x-ray apparatus that has the shape of at least part of a dental arch.
It is an additional object of the present invention to provide an intraoral digital x-ray apparatus that requires little skill to operate.
It is yet an additional object of the present invention to provide an intraoral digital x-ray apparatus that reduces or eliminates entirely the gag-reflex associated with conventional intraoral x-ray apparatus
Additional objects and advantages of the present invention will become apparent as the description proceeds.